Using game theory in primates to study the distributed neuronal and time- causal underpinnings of interactive social behavior Despite the importance of joint interactive social behavior and its broad involvement in many neurocognitive disorders, its single-neuronal basis, population-level encoding and time-causal underpinnings are still largely unknown. A major part of this limitation has come from our inability to ask such questions in humans. Game theory, and the iterated Prisoner's Dilemma (iPD) game in particular, provides a well-studied platform for investigating and dissociating the multi-dimensional encoding of interactive social decisions. Here, we will build on recent innovations by our group with dual interacting primate-pairs, neural population recording and deep brain stimulation (DBS) in order to systematically investigate the basic neuronal building blocks of interactive social behavior. In preliminary studies performed by our groups, we have already identified some of the key neuronal computations underlying joint social decisions. We have also established important behavioral validation measures, social context controls and cross-pair confirmations for the primate model. In this study, we will investigate, for the first time, the involvement of three principal areas theorized to comprise the ?social brain? in distributively encoding and modulating distinct aspects of interactive social behavior. These areas include the dorsal anterior cingulate cortex, anterior intraparietal area and the basolateral amygdala. We will specifically examine the single-neuronal and population encoding of self vs. other agency, joint interaction, social context and agent identity. We will test how these representations are modulated by social cues and examine the targeted modulation of the different areas by both standard and event-triggered DBS. Overall, this proposal represents a completely new line of investigation that is not possible to conduct in humans, and opens up an important unexplored area in neuroscience. The proposed set of studies will provide the first comprehensive roadmap of the primate ?social brain? at the neuronal and population level, and offer critical guidance for future targeted treatments of social behavioral disorders.